The strip packages advantageously allow each product to be hermetically sealed. Information concerning the product contained in the strip package can be printed and/or coded on the relative package, such as for example packaging and expiry dates, product composition, dosage and use instruction, etc.
This kind of package is particularly indicated for effervescent products, particularly sensitive to humidity, and generally, for pharmaceutical products.
The strip packages are obtained from two sheets of heat-weldable material, which are placed one over the other, touching each other, and which form a plurality of suitably spaced apart pockets for containing single products.
The pockets are suitably welded along the peripheral edges, so as to make them hermetic and sealed.
Pre-breaking areas, facilitating detaching of the single pocket from the package, are defined by pre-cuts made in regions corresponding to the welded areas comprised between the adjacent pockets of the same longitudinal row, or to an adjacent row.
In accordance with the required specifications, the strip packages can include one single pocket containing the respective product, or a plurality of pockets, usually arranged in one or more longitudinal rows.
Known machines for strip packaging of products extend substantially vertically and, in most cases, they are operated in a continuous operation cycle.
A feeding station is situated in the upper portion of these machines, for feeding products, in a way widely known to those skilled in the art, to a packaging station, situated below, in cascade, where the products are placed and sealed in the respective pockets.
The packaging station includes a pair of counter-rotating welding rolls, having horizontal and parallel axes, touching each other along a common generatrix, and acting together on two sheets of weldable material, which unwind from respective reels, situated opposite to each other and on both sides with respect to the welding rolls.
Each of welding rolls has, on its outer surface, a plurality of axially and angularly equidistant radial recesses, which match corresponding radial recesses of the adjacent roll during the synchronous rotation of the rolls. In this way, a series of cavities are formed for housing the products supplied by the feeding station.
The products are first released and placed in the cavities, where they are covered by sheets, which pass and turn over the welding rolls, to define the containing pockets, which are then welded along the peripheral edges thereof, thus obtaining hermetic and sealed packages.
The peripheral edges of the recesses of each welding roll, in particular of the areas of the outer surfaces comprised between adjacent recesses, are heated by relevant groups of electric heating elements, suitably distributed. The temperature produced by the heating elements is constantly measured by suitably situated thermal probes.
Therefore, a continuous strip of welded pockets is obtained at the outlet of the pair of counter-rotating welding rolls.
The packaging station includes, arranged in cascade with the welding rolls, symmetrically thereto, a pair of lower counter-rotating rolls, having horizontal parallel axes, touching each other along a common generatrix, aimed at drawing the obtained continuous strip away from the packaging station.
Downstream of the packaging station, that is downstream of the pair of lower rolls, there is a working station, which, according to a continuous operation cycle, performs the following operations: ink jet printing on each pocket; codifying obtained by dry-stamping with a die and a relief; checking, by suitable feeler pin means, the presence of the products inside each sealed pocket; precutting, crosswise with respect to the forward movement direction of the strip of welded pockets, by means of pre-cutting groups; longitudinal cutting to obtain longitudinal rows by first cutting groups; crosswise cutting of each longitudinal row by second cutting groups.
The so obtained strip packages, formed by a predetermined number of pockets, are moved along slide conveyors, which, due to gravity, space them apart, in random way, and send them to belt conveyors situated nearby, usually arranged at 90° with respect to the feeding direction of the feeding station.
The main drawback of this type of packaging machines lies in the fact that it is necessary to add an auxiliary machine, positioned in cascade with the described one, for allowing feeding of a packaging machine, which is capable of introducing the so obtained strip packages into cases, usually of paperboard.
This derives from the fact that the packages leaving the working group, suitably printed, verified, codified, pre-cut and cut, are placed, by the slide conveyors, on the belt conveyor in a non-controlled configurations, which is not suitable for direct feeding of a packaging machine.
Another drawback results from the considerable vertical extension of the known machines, which does not allow the operator to see correctly critical areas, such as the printing and die-stamping areas, to verify that the information are well printed on the packages. Another critical area which is not well seen by the operator is the welding rolls inlet area, so that the correct feeding of the products and best positioning of the sheets at the inlet cannot be easily verified.
Conventionally, this drawback is avoided by using a mirror, however, they allow only a non direct visual control, and is not particularly reliable and easy for the operator.
A further drawback of the traditional machines for producing strip packages derives from the fact that, if the feeler means detects an anomaly, selecting means reject the whole transversal row of strip packages.
Consequently, also strip packages which have given positive result from the verify, are rejected together with anomalous packages (caused by lacking of one or more products in the relative cavities) present in the same transversal row, which causes a reduction in the production rate.